Cadmium electrodeposition



July 6, 1937. J. v. VAUGHEN 2,085,776

CADMIUM ELECTRODEPOSITION Filed oct. 17, 1955 Aldacets K@ zwldnes Amine Amine L r.. J

Kecldone- A'mlne Reaction Product Aldace- Amine Reaction Product INVENTOR.

JOHN V. VAUGHEN.

ATTORNEY.

Patented July 6, `1937 CADMIUM ELEc'raom-:PosrrroN John V. Vaughen, Lakewood, Ohio, assignm, by meine assignments, to E. I. du Pont de Ne mours & Company. Wilmington, Del., a corporation of Delaware Application october 17, 1935, serial No. 45,591

17 Claims.

L This invention relates to the electrodeposition of cadmium from cyanide-cadmium baths, and is particularly directed to cyanide-cadmium plating compositions, plating baths, and plating 5 processes which employ, as an addition agent, a

ketaldone-amine reaction product whereby a bright, smooth, uniform cadmium deposit 'is obtained. Y A

It has heretofore been proposed to modify the l character of cadmium deposits by the use of organic addition agents' such -as sulflte cellulose waste, dextrin, starch, alkylated naphthalene sul-` fonic acids, wool, caffeine, shellac, casein, licorice, glucose, alkali reaction products of heterocyclic l aldehydes, furfural gum arabic, and gelatine.

It has been necessary to employ anaddition agent and/or a brightener with cyanide-cadmium plating baths, because, without such modifying agents, cadmium deposits of exceedingly p'oor v' character and appearance are obtained.` The properties of electrodeposited cadmium are large- .ly determined by the addition agent and/or brightener used, and the desirability of a cadf mium plate is, to a great extent, dependent upon the elcacy-of the modifying agents employed..

'Ihe properties of a cadmium plate arepartly dependent, incommercial practice, upon certain characteristics of the plating bath employed, and these' characteristics can be modified, to some extent, by suitable organic addition agents and/or brighteners. Under strictly controlled conditions, one can deposit a fairly satisfactory cadmium plate on a i'lat cathode with a' bath which, in ordinary commercial practice, would be unsatisfactory. Under the usual conditions of commercial' operation, particularly when recessed articles or articlesof irregular -shape are to be plated, y a bath must have a fairly wide bright current density range and good throwing power ifeven moderately satisfactory results are to be obtained. 'I'he throwing power and the extent of Y the bright range have been somewhat improved by the use of the addition agents' heretofore known.

have effected a considerable'improfv'ement in processes for the electrodeposition` of cadmium,

be desired.

the results obtained have not been all that could 5:f as a bright, smooth, lustrous', ducale, adherent While the addition agents hitherto employed v I have found that amine derivatives of' yketel- .dones are exceedingly effective additionagents- By theI use of thesefnovel addition agents, itis possible to elecdeposit. Baths containingt'hese novel addition agents are characterized by good throwing power and by a wide bright current density range.

In the accompanying drawing there are shown the relationships existing between various deriy- 5 atives which constitute the addition agents of my invention, land there are also shown, diagrammatically, the methods of preparation oi!-` the various derivatives.

Represented by a circle in-,the'upper left-hand 10 y corner of the drawing are lthe starting materials from which my addition agents are derived. The starting materials are designated ketaldones but, as will become apparent hereinafter, the best results are obtained by the use of certain alii5 phatic and carbocyclic aldehydes and ketones.

I have applied the term ketaldonyl, to designate the C=O group as it appears in aldehydes and ketones -in contradistinction to the C=O group as it appears in acids. "Of course, the carbonyl group as it 'appears in acids,

is very different in its properties from the carbonyl groupas it appears in aldehydes and ketones, and the expression ketaldonyl group is employed lto distinguish lthe aldehydic and the ketonic carbonyl group from the acidic carbonyl group. `Theexpression. ketaldonyl group\as used herein designates a carbonyl group in which a third carbon valence is joined to carbon-and in which the remaining valence is satisfied by car bon or by hydrogen. 0r, in chemical symbols, the ketaldonyl group as used herein is of the type wherein R. is a hydrocarbon radical and wherein -R' is hydrogen, in the case of an aldehyde, or

-`. sulfur,'and which do not contain nitrogen. The' 55 starting materials, moreover, should contain no more than two hydroxyl groups and preferably should contain at least two carbon atoms. More specifically, I prefer to employ ketaldones which contain only carbon, hydrogen, and oxygen, which contain at least two carbon atoms, and in which the hydrogen-oxygen ratio is greater than that of water. i

As is illustrated in the drawing, the starting materials, the ketaldones, are reacted with an amine, in alkaline solution, to produce a ketaldone-amine reaction product.

A preferred group of ketaldones, the aldacets, are illustrated in the upper right-hand corner of the drawing. More will be said hereinafter re garding the members of the illustrated aldacet equilibrium. As is shown in the drawing, the aldacets, like the ketaldones generally, are reacted with an amine to produce a ketaldoneamine reaction product.

'I'he aldacets comprise the aliphatic aldehydes: acetaldehyde, aldol, crotonaldehyde, and paraldol. In dilute alkaline solution the aldacets-appear to exist in equilibrium, any one of the aldacets leading to the production of all at a rate of conversion apparentlydepending upon the speciilc aldacetrst present. The aldacet equilibrium is illustrated in the upper, right corner of ,the drawing.

Referring to the aldacet equilibrium in more detail, it is noted that acetaldehyde in dilute a1- fkaline solution is quickly converted to aldol thus:

H H H H H H H H m H l-l.--.----l -o ...ideals o ..--.H/ H

'The aldol may lose one1 molecule of water and become crotonaldehyde, thus:

III H H H H (a) n-c-flJ-o l:=o s: H-f-ho- =o The aldol may condense to form paraldol, thus: c) (cimoi) (amaca.

The n in Equation 3 is a whole number, probably 2.

In order to visualize the relationships existing between the aldacets, reference should be had'to the accompanying drawing wherein these rela-- tionships are diagrammatically illustrated. It is to be understood that the relationships are shown may lose water and go to crotonaldehyde, though this latter conversion probably takes place to a.

very small degree. The crotonaldehyde may form from acetaldehyde, aldol, or paraldol, and, by

gaining water, may revert to any of them, though it is likely that it Wouldmove largely by way of aldol. l

As is seen in the drawing, then, we may`consider the aldacets as being in equilibrium. This equilibriumfwill, according to my belief, be substantially the same regardless of which of the four solution form this aldacet equilibrium rather slowly or move more rapidly in certain directions than in others.

While I have mentioned only acetaldehyde,

aldol, crotonaldehyde, and paraldol as members of this sub-genus, I'may use any condensation product of acetaldehyde in dilute alkali solution. Another aldacet is paraldehyde. Ordinarily paraldehyde is considered as forming only in acid solutions, but I have reason to believe that at least some paraldehyde forms in the discussed aldacet equilibrium. Paraldehyde is apparentlyv very slow to convert to other aldacets and probably because of this fact is none too satisfactory a starting material.

Aldol, acetaldehyde, crotonaldehyde, and paraldol are the only commercially available aldacets at the present time. For practical -reasons, therefore, I prefer to use as a starting material, an aldehyde selected from the group consisting of acetaldehyde, aldol, crotonaldehyde,

` kaline solutions. It will be understood that the aldacets include the equilibrium products as above described, and that they do not include l irreversible condensation products which may not reversibly lead to the formation of the aldacet equilibrium.

As a definition for the purposes of this application, then, the aldacets are reversible equilibrium-.condensation products of acetaldehyde in alkaline solution, and particularly in alkaline solutions such as those of the following Example I.

lAs will be noted in ldetail hereinafter, the' aldacets are not entirely equivalent for my purposes but are substantially so. Crotonaldehyde, for example, seems to lead to slightly lower yields. This may be attributable to the fact that crotonaldehyde is but slowly converted to the necessary form, or to some other now unknown cause.

As is above mentioned, there is considerable uncertainty as to the extent and nature of the conversion of some aldacets to others. All of the evidence now available `to me substantiates the putative theory above advanced as to the nature of the aldacet equilibrium, but it will be understood that direct experimental evidence is obtainable only with great diilculty. In most instances the aldacet equilibrium exists for only a short time, some further action quickly taking place to form resins. That the aldacets are in some kind of equilibrium Ais relatively certain, but` the proportions of individual aldacets and the rates of conversion have, to date, defied exact determination. v

It is clearly to be understood that the above description of the relations between the initial materials is for purposes of illustration and that I do not intend to be limited in any way' thereby, because the chemistry of these compounds is intricate and obscure, and because my results are obtained entirely apart from theoretical considerations.' It is also to be understood that whilel refer to aldol, acetaldehyde, crotonalde- `.known form and then react.

lines.

2,085,776 hyde, and paraldol -as resulting from the condensation of acetald'ehyde in alkaline solutions, I do not wish to be limited thereby, as I may use aldol, acetaldehyde, crotonaldehyde, and paraldol which have been made in any manner.

Turning now Ato a consideration ofthe ketaldone-amine reaction products produced from the aldacets, -it is rst noted that the term reaction" is used to express whatever occurs when the ke- ;taldones, or specifically the aldacets, are treated with an amine. The term reaction" is used to distinguishfrom condensation as lused above with reference to the aldacet equilibrium tho, in

the remaining aldacets move towards the re- 1 moved 'materials' to restore the equilibrium, and

are so all finally utilized.

To illustrate the production of theaddition agents of my invention, the following specic examples are given:

ExAMPLmI Equimolecular proportions of crotonaldehydeand I nonoethanolamine were reacted, starting the reaction at room temperature. The temperature of the mixture was held at about iorty'to vilfty degrees centigrade until no further reactionwas apparent. The reaction mixture was a A plating solution was made up and usedin the ployed as an addition agent in a reddish-brown, viscous liquid, readily soluble in cyanide-cadmium plating baths.

Theaddition agent ofthis example was emcyanide-cadmium bath made up as follows:

Bath (1) Grams per liter Sodium cyanide (NaCN) 130 Cadmium oxide (CdO) 43 Sodium sulfate (NanSOD 50 Cobalt sulfate' (00804-711140) 10 Addition agent l 1.2

customary way to plate a numberof articles with a cadmium deposit about fivethousandths ofan inchthick. After washing with water; the articles were examined and found to have a perfectly smooth, mirror-like nish. It is, of course, very dilcult with prior art processes to obtain even a fairly smooth finish when so thick a deposit of ycadmium is plated.

The bath of this example displayed good throwing power and a wide bright current density range. The product of -this example may satisfactorily be employed in widely varying amounts, but I usually prefer` to use between about eight--4 tenths and two grams per liter. 'I'he proportion of the agent used above, one and two-tenths' grams per liter, is about an optimum under the conditions of this example. Y

The following specific example illustrates the use of the product of this example as an addition agent in a dilute b'ath:

'I'his bath was used for plating several objects at acurrent density of twenty amperes per square foot.' The deposit was extremely bright and smooth. -Thenumber of grams of cadmium oxide inthe above bath may be varied bet'ween iifteen and thirty-tive and good results will be obtained. If the bath be too concentrated the deposit will not be entirely satisfactory.

The addition agent is used in about an optimum proportion for the conditions of this example, but I may advantageously employ from about ve-tenths toA about seventy-five hundredths gram per liter of this agent.

-While my addition agents are eiective in any customary cyanide bath, I prefer to use baths of the kind set forth in U. S. Patent 1,681,509 to Mr. Leon R. Westbrook, and in Bath (l) These baths are of the cyanide type, and contain a small amount of a compound of a metal of the iron group having an atomic weight greater than nity-eight. The details as to the formulation and use of these baths may be found in the said Patent 1,681,509 andneed not be duplicated The plating baths of the said Patent 1,681,509 .are modiiied only by employing my novel addition agents in lieu o f the addition agents, goulac,

dextrin, starch, etc., mentioned therein. While .the plating processes described in the said Patent 1,681,509 lead to a. bright, hard, dense,- and smooth deposit of cadmium, and while the in- -vention therein described and claimed has been widely accepted -by the art because of its merit, the substitution of .my addition agents for those in the patent results in .a cadmium deposit of even greater smoothness, uniformity, and bright- 1185s. 'i V Of course, I may use other compounds of metals of the iron group having an atomic weight greater than fifty-eight,` such as nickel, copper, etc., as disclosed in the heretofore mentioned Patent 1,681,509, but the use of cobalt compounds, as in Bath (1), has led to the best results.

I desire that it be clearly understood that the whole disclosure of the heretofore mentioned Flat'- ent 1,681,509, aswell as that ot U. S. Patent 1,564,413 to ClaytonM.` Hoff, cited therein, is to be considered; in its entirety. as an integral part oi my disclosure, vas my novel addition'a'gents co-act with the cyanidefmeta'l compound baths therein tol produce a result unexpected 'from an tion agents or the baths of the said patent.

WhileI havev discussed above the use of baths of the Westbrook type, I do not wish to be ylimi ited thereto. I prefer tousethem because of certain commercial considerations', and because they may b more concentrated-but excellent results are obtainable with other. types of baths, such as Bath (2) above.

EXAMPLE II A reaction product similar to that of Example AI was produced by reacting equimoiecular proportions of aldol and mono'ethanolamine. AA product exceedingly similar to the one of Example I was produced, and comparable results were -obtained when the product of this example was 'Bam (2) Grams per liter Cadmium oxide (CdO)v 26 i Sodium cyanide (NaCN) 87 f Addition agent 0:1 5

examination of the attributes of leither my addiused as an addition agent in cyanide-cadmium plating baths of the type shown in Example I.

EXAMPLE III` One-half mole of monoethanolamine and one mole of aldol were reacted at temperatures between 30 and 40 C. Th product was not as soluble as the product of E mple II, and it was not as satisfactory an addition agent for use in cyanide-cadmium plating.

' EXAMPLE IV Equimolecular proportions of aldol and diethanolamine were reacted to room ltemperatures. A product very similar to those of the above examples was produced, the product of this exam- .ple, however, being slightly less soluble than the product of Examples I-and II.

The product of this example and some of the hereinafter mentioned products are not-readily soluble in cyanide-cadmium plating baths, and it is desirable that they be dispersed in the baths. It is expedienbto disperse the addition agent if diiculty is encountered in dissolving an optimum quantity. The addition agents may be dispersed and their dissolution aided by adding them to a cyanide-cadmium bath in a suitable solvent, such as alcohol or acetone. It may sometimes be found desirable to reduce the addition agen-ts tol a finely divided state, or to use them in conjunction with such dispersing agents as saponin, gum arabic,

and sulte cellulose waste.

EXAMPLE V Equimolecular proportions of aldol'and Atriethanolamine were reacted at room temperatures. 'I'he reaction product of this example was somewhat less soluble than the products of Examples I and II. While the product of this example caused the production of a very bright deposit when added to a cyanide-cadmium plating bath, the bath had a more restricted bright current density range than when the products of Examples I and II were used.

While I have shown-the reaction of the aldacets with certain amines in the above examples, it will be understood that other amines may be used. I may, for instance, prepare'addition agents by treating the aldacets with amines such as the glucamines, for instance, glucamine and methyl glucamine, or aliphatic amines, f or instance. methyl ethylamine, methylamine, and ethylamine.

While the aldacet-amine reaction products may be prepared byconductingthe reactions of the above examples at ratherwidely varied temperatures. I prefer that` the reaction be performed at temperatures between about thirty and fifty degrees centigrade. If much lower temperatures be maintained, the reaction products will tend to contain insoluble or relatively inactive constituents. Similarly, the reactionv temperatures should not be permitted. to rise too high, because, when the reaction proceeds at high temperatures, the reaction product may contain insoluble constituents and may have none too great an efiiciency as an addition agent.

It is generally preferredto employ an equimolecular proportion, or an excess, of amine to, aldehyde. As will be noted by comparing Examples lI and III, less satisfactory amaldacets. are pro- 'duced when less than an equivalent amount of "ai'nineis used.

In the foregoing, the products derived'by re- ,acting an aldacet with an amine have beenl discussed in some detail with reference to thei:

preparation, their properties,` and their applica tions as addition agents in 4cyanide-cadmium plating. The products thus considered above are, in many respects, typical of the addition'agents of my invention.

The above products are, of course, derived from certain aliphatic ketaldones: the aldacets. Below are discussed typical ketaldone-amine reaction products derived from other aliphatic ketaldones and from carbocyclic ketaldones.

The following typical aliphatic ketaldones were tried as starting materials for the production of addition agents. 'I'he aldacets are included for purposes' of comparison. The compounds in the respective lists are given in about the order of their desirability as starting materials.

f Aldehydes 1. Aldol 2. A'cetaldehyde 3. Crotonaldehyde Paraldol Propionaldehyde a-ethyl -.propyi acrolein Butyraldehyde Acrolein .`Citral Citronellal Hexadecoic aldehydel .Isobutylaldehyde i Ketohe ExAMPLn VI v Equimolecular proportions of monoethanolamine and propionaldehyde were reacted at room temperature. A soluble resin was obtained which,

@ceden-nennenwhen employed in baths such as those of Example I, displayed activity as an addition agent but was none too satisfactory, v

" ExAnLn'VII Methyl ethyl ketone was treated at about 40 4to 50 C. with diethanolamine in equimole'cular proportions. The resulting reaction product displayed activity as an,` addition agent in cyanidecadmium plating baths.

When aliphatic ketaldones are used as starting l materials,4 a. ketaldone should be selected whichcontains at least two carbon atoms. Formaldehyde, with but one carbon atom. stands in a uniquevposition with respect to valdehydes -gen erally. Its dissimilarity to the other aldehydes is, of course, generally recognized, and it does .not lead to the production of entirely satisfactory addition agents.

In view of the difference between formaldehyde and other aldehydes, one would expect formaldehyde to behave dierently as a starting material for the production. of addition agents.

2,085,776 'As addition agents prepared from formaldehyde are of a diierent order of eilectiveness and are of a different 'character from the agents prepared from other aldehydes, I prefer to employ ketaldones which have more than one' carbon atom.

As the aliphatic ketaldones contain more and more carbon atoms, they appear to become less desirable as starting materials for the p roduc-` tion oi amketaldoresins. Citral and citronellal,

,aliphatic ketaldones containing between two and nine carbon atoms. This terminology includes acetaldehyde, for example, as a two carbon atom compound and citral as a nine carbon atom compound. I especially prefer to employ those alisoV vketaldones have been discussed above in some phatic ketaldones of two to nine carbon atoms which contain no more than two hydroxyl groups. I have found that it is not desirable that the aliphatic ketaldones contain carboxyl groups.

Moreover, the elements sulfur and nitrogen are preferably absent from the aliphatic ketaldones which I employes starting materials for the production of my addition agents. I especially pre` fer to use aliphatic ketaldones which contain only carbon', hydrogen,'and oxygen, and in which the hydrogen-oxygen ratio is higher than that of water.

While, as is above noted, I prefer that the aliphatic ketaldones which I employ as 'starting materials contain no more than two hydroxyl groups, and, more specically, that they have a higher ratio of hydrogen to oxygen than that of water, it is, nevertheless,'within the scope of my present invention to use such ketaldones as ketoses and aldoses.

When carbohydrates which containan aldehyde or ketone group are treated with an amine, products similar to those above may, with some difficulty, be prepared. The products thus produced, however, are of a different order of effectiveness from the preferred products.

The products prepared from the aliphatic detail, and it is now proposed to discuss briefly' the preparation of ketaldone-amine reaction products from carbocyclic ketaldones.

The following carboc-yclic ketaldones, tried as starting materials for the production of ketaldone-amine products, are listed in the approximate order of their desirability.'

1. Cyclohexanone Methyl cyclohexanone Benzoin Benzaldehyde Anisic aldelrvde Cinnamic aldehyde Quinone Vanillin Ortho-ortho dicarboxy benzoin In order more fully to describe the production of addition agents from the carbocyclic ketaldones, the following illustrative example is given:

@Memes Equimolecular proportions oi.' monoethanolamine and benzaldehyde were reacted'at about 40 to 50 C. The product displayed activity as an addition agent in cyanide-cadmium plating baths of the types shown in Example I.

The other carbocyclic compounds above listed may be similarly treated with an amine according to the above procedures with good results.

While generally I may advantageously employ any carb'ocycllc ketaldone. I prefer to use as starting materialsketaldones which do not contain a carboxyl group and which do not contain sulfur. Moreoverycarbocyclic ketaldones which do not contain nitrogen are ordinarily preferred, because while Michlers ketone, for instance, responds to my broadest definition, it is none too satisfactory a starting material.v Speciiically, I prefer to employ carbocyclic ketaldones which contain only carbon, hydrogen, and oxygen and in which the hydrogen-oxygen ratio is greater than in water.

The foregoing discussion of the aromatic ketaldones is limited to a preferred group, the carbov cyclic .ketaldonea It will be understood, however, that my invention in its broad aspects includes the use of cyclic ketaldones generally. I may, forinstance, use heterocyclic ketaldones. such as furfural, as starting materials for the preparation of addition agents for cyanide-cadmium plating baths.

In order conveniently to merchandise my novel addition agents, I may incorporate them with the dry ingredients -employed to makeup a plating bath. The resulting dry mixture can then be packaged and'sold to theconsumer who needs vonly to dissolve the mixturein water for use. Again, I may nd it desirable to incorporate the j addition ag'ent with only one or a few of the ingredients and let the consumer add the other ingredients. Frequently, of course, it will be desirable to merchandise the novel addition agents as such.

While I have disclosed a number of speciilc cyanide-cadmium baths heretofore, it will be understood that I do not intend to be limited thereby and that the teachings of my invention xarliay be applied to cyanide-cadmium baths gener- It will be also understood that I do not intend to be limited to the speciiic ketaldone-amine reaction.

products above disclosed, as numerous other such compositions can readily be. prepared by those skilled in the art according tothe principles o! Containing an amine reaction product oi a carbocyclic ketaldone. 1

3. A cyanide-cadmium plating composition containing an amine reaction product of an aliphatic ketaldone.

4. A cyanide-cadmium plating composition containing an amine reaction productof an ali-` phatic ketaldone which contains only carbon, hydrogen and oxygen, which has no less than two and no lmore than nine carbon atoms. and in which the ratio of hydrogen to oxygen is greater than that of' water.

5. A cyanide-cadmium plating composition containing an amine reaction product o! an aldacet, an aldacet being, as herein set forth, one of '6 the aldehyde equilibrium products which results when acetaldehyde is put in alkali metal cyanide solution.

6. A cyanide-cadmium plating composition' 5 containing an amine reaction product of an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, crotonaldehyde, and paraldol.

7. A cyanide-cadmium plating composition lo containing an amine reaction product oi' aldol.

8. A cyanide-cadmium plating composition containing an ethanolamine-reaction product of an aldacet, an aldacet being, as herein set forth,

one of the aldehyde equilibriumproducts whichl5 result when acetaldehyde is put in alkali metal cyanide solution.

9. In a process for the electrodeposition of cad' mium, the step comprising depositing cadmium from a cyanide-cadmium bath which contains a 20 metal oi the iron group having an atomic weight greater than fifty-eight, andan amine-reaction 35 mium from -a cyanide-cadmium bath in the pres-A ence oi an addition agent comprising an amine reaction product of arr aliphatic ketsldone.

13. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising an amine reaction product of an aliphatic ketaldone which contains only carbon, hydrogen and oxygen, which has no less than two and no more than nine carbon atoms. and in which the ratio of lrvdrogen to oxygen is greater 'than that of water.

14..In a process for the electrodeposition of cadmium. the stepcomprising depositing cadmium from a cyanide-cadmium bath in thepres-1 ence of an addition agent comprising an amine reaction product of anvaldacet, an aldacet being, as herein s'et forth, one of the aldehyde dehyde is put in alkali metal cyanide solution.

15. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agentcomprising an amine reaction product of an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, crotonaldehyde, and paraldol. 18. In 'a 'process for the electrodeposition `o cadmium. the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising an amine vreaction product of aldol.

17. In a process for the electrodeposition 'of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the pres- Y ence of an addition agent comprising an ethanolamine-reaction product of an aldacet, an aldacet being, as herein set forth, one of the aldehyde equilibrium products which resultwhen acetaldevhyde is put in alkali metal cyanide solution.

JOHN V. VAUGHEN.

' equilibrium products which result when acetal- 

